Photoelectric devices, e.g., LED, made of nitride material system are widely applied in fields like solid display, lighting and signal light for the band gap of such material can cover entire visible light range. The non-toxic nitride material has such advantages as high luminance, low work voltage and easy for miniaturization. Therefore, replacement of traditional light source with GaN-based LED has become an irreversible trend. However, one of the keys to obtain nitride light emitting device of higher luminous efficiency lies in improvement of photoelectric conversion efficiency and extraction efficiency.